This invention relates to a process for filling a muffler shell with fibrous material.
U.S. Pat. No. 4,569,471 to Ingemansson et al. describes a process and apparatus for feeding lengths of a continuous glass fiber strand into a muffler outer shell. The apparatus includes a nozzle for expanding the fiber strand into a wool-like material before the material enters the outer shell. In a first embodiment, filling of an outer cylinder 14 of the muffler shell occurs without an end-piece joined to the outer cylinder 14. After the filling operation is completed, the outer cylinder 14 is moved to a separate station where the end piece is welded onto the outer cylinder 14. In a second embodiment, illustrated in FIG. 3, a perforated pipe/outer end piece assembly is positioned only part way into the muffler outer cylinder 14 during the glass material filling operation. After the filling operation has been completed, the perforated pipe/end piece assembly is moved to its final position within the outer cylinder 14.
The ""471 patent process is acceptable when filling a muffler shell of the type including a separate end piece or perforated pipe/outer end piece assembly. However, the process is typically not used with clam shell mufflers comprising first and second halves which, when coupled together and enclosing a perforated pipe, do not have an open end through which fibrous material may be fed. Some clam shell mufflers include internal plates which are positioned in face-to-face relationship and located between outer shell parts; see for example U.S. Pat. No. 5,859,394.
It is also known in the prior art to form preforms from glass material which are adapted to be inserted into a first muffler shell section prior to it being coupled to a corresponding second shell section; see U.S. Pat. No. 5,766,541, the disclosure of which is incorporated herein by reference. While such preforms are acceptable in performance, they add additional cost to the muffler due to the manufacturing steps necessary to form the preforms.
Hence, there is a need for an improved, low-cost muffler outer shell filling process which can be used to fill muffler shells such as clam-type muffler shells.
This need is met by the present invention, wherein a process is provided for filling a clam-type muffler shell using a form having open ends. The form is placed over one muffler shell part and/or an internal shell structure such as a pair of internal shell plates, which define at least one channel. The form is filled with a fibrous material. Thereafter, the form is removed and another muffler shell part is placed over the one part and/or the internal shell structure. The form defines a temporary container or mold for the fibrous material. A partial vacuum is preferably drawn through the channel during this process such that the fibrous material is pulled inside the form and later within a cavity defined by the muffler shell parts. It is noted that as the other muffler shell part is brought into contact with the one part and/or the internal shell structure, an increase in air velocity between those parts occurs due to the vacuum. The increased air velocity results in any glass fibers extending out beyond the edges of the shell parts and the internal shell structure being pulled inwardly inside an inner cavity of the muffler shell.
In accordance with a first aspect of the present invention, a process is provided for filling a muffler shell with fibrous material comprising the steps of: providing a muffler shell comprising first and second muffler shell outer parts which define an internal cavity when coupled together and an internal structure adapted to extend at least part way through the shell internal cavity for defining at least one channel having one or more openings communicating with the shell internal cavity; placing a form over at least one of the internal structure and the first muffler shell part; drawing a partial vacuum through a first end of the channel; feeding fibrous material into the form while drawing a partial vacuum through the channel; removing the form after the fibrous material feeding step; and positioning the second muffler shell part over at least one of the internal structure and the first muffler shell part.
The partial vacuum may also be drawn through the channel after the form is removed and during the positioning step.
The form may comprise a structure having upper and lower open sections and an outer perimeter shaped like that of one or both of the first and second shell parts.
The feeding step may comprise the steps of: providing a nozzle; feeding continuous strand material and pressurized air into the nozzle such that a wool-type product emerges from the nozzle; and positioning the nozzle adjacent to or in the form such that the wool-type product is fed into the form.
In a first embodiment, the internal structure comprises one or more perforated pipes which define one or more channels. In a second embodiment, the internal structure comprises a pair of stamped plates in face-to-face relationship which define the at least one channel. The stamped plates may be coupled together before or after the feeding step. The plates may be welded together, bolted together, or coupled together using any other conventional coupling arrangement.
The positioning step may comprise the step of positioning the second muffler shell part over the plates. The method may further comprise the steps of placing the plates over a deformable panel prior to the feeding step and removing the plates from the deformable panel after the second shell part has been positioned over the plates.
The placing step may comprise the step of placing the form over a first side of the pair of stamped plates. The method may further comprise the steps of: placing the form over a second side of the pair of stamped plates; drawing a partial vacuum through the first end of the channel; feeding fibrous material into the form while drawing a partial vacuum through the channel and with the form over the second side of the plates; removing the form after the fibrous material feeding step; and positioning the first muffler shell part over the plates and the second muffler shell part.
The process further comprises the step of coupling the first and second muffler shell parts together.
In accordance with a second aspect of the present invention, a muffler is provided which is filled with fibrous material in accordance with the process comprising the steps of: providing a muffler shell comprising first and second muffler shell outer parts which define an internal cavity when coupled together and an internal structure adapted to extend at least part way through the shell internal cavity for defining at least one channel having one or more openings communicating with the shell internal cavity; placing a form over at least one of the internal structure and the first muffler shell part; drawing a partial vacuum through a first end of the channel; feeding fibrous material into the form while drawing a partial vacuum through the channel; removing the form after the fibrous material feeding step; and positioning the second muffler shell part over at least one of the internal structure and the first muffler shell part.
In accordance with a third aspect of the present invention, a process is provided for filling a muffler shell with fibrous material comprising the steps of: providing a muffler shell comprising first and second muffler shell parts which define an internal cavity when coupled together and an internal structure adapted to extend at least part way through the shell internal cavity for defining at least one channel having one or more openings communicating with the shell internal cavity; placing a form over at least one of the internal structure and the first shell part; drawing a partial vacuum through a first end of the channel; feeding fibrous material into the form; removing the form after the fibrous material feeding step; and positioning the second muffler shell part over at least one of the internal structure and the first shell part.
The partial vacuum may be drawn through the channel during the fibrous material feeding step, after the form is removed and during the positioning step.